The nucleocapsid (NC) protein p7 from HIV-1 is required for packaging of genomic RNA. The protein (55 residues) contains two zinc fingers and a single Trp residue that is involved in nucleic acid binding through stacking interactions with nucleobases. We have characterized the lifetime and dynamic anisotropy properties of metal free and bound to various divalent ions (Zn2+, Cd2+, Co2+) and in complexes with DNA and RNA oligonucleotides. Perturbations of the Trp fluorophore upon oligonucleotide binding are being investigated to provide a model for the interaction of intercalating aromatic residues with nucleic acid lattices. A series of truncated and point mutated sequences have been used to show that there is a transient interaction in which the two zinc fingers are in close proximity. These studies are being extended other HIV-1 proteins (reverse transcription integrase) as well as to nucleocapsid proteins isolated from different retroviruses (SIV, HTLV-1)